1. Field of the Invention
The present invention relates to the calibration of a robot, and more particularly to a calibration tool and method that provide a standard and efficient calibration process.
2. Description of the Prior Art
In current semiconductor fabrication, different processes such as etching, doping etc. require different machines. Therefore, it is necessary to move wafers between cassette and process chambers.
Obviously, when a wafer is moved from a cassette to a machine, a robot is used to catch the wafer and move the wafer to these process chambers of the machine. It is important that the robot must hold analogous positions of different wafers in the same position. Otherwise, because processes such as photolithography and etching are sensitively dependent on the position is of chips of the wafer, the yield of the machine is decreased. Beside, the robot must catch the wafer at the optimized positions, i.e. the relative position between the wafer and the robot must situate in the predetermined working range of the robot. Otherwise, deviation of the relative position increases the risk that the wafer collides with the machine and is damaged or even broken.
Because the wafer is not transparent, it is difficult to adjust the relative position to the predetermined working range. On the other hand, because the wafer comprises a plurality of chips it is unsuited to make any label on the wafer. Thus, accuracy of the relative position between the wafer and the robot is unfavorable and the yield of the machine is decreased.
According to the previous discussion, it would be desirable to provide a robot calibration tool and a robot calibration method that may be used to provide an efficient and accurate robot calibration process.